It is known in the art to use old and scrap roofing shingles in the manufacture of asphaltic paving composition. One such method is disclosed in U.S. Pat. No. 4,706,893. In this and other methods, it is necessary that the shingles be shredded or otherwise reduced in size so that they can be more accurately weighed and metered.
The '893 patent discloses a method and apparatus for recycling asphalt shingles in an asphalt plant which combines virgin aggregate with liquid asphalt to form an asphalt paving composition. The shingles are comminuted into particles and the shingle particles are introduced into the asphalt plant such that they are heated to melt the asphalt in the shingle particles. The virgin aggregate, shingle particles, and liquid asphalt are thoroughly mixed to form an asphalt paving composition.
It is appreciated in the '893 patent that the shingles tend to stick together in a pile, which can lead to problems during processing. Col. 4, lines 53-62. However, experience has shown that merely comminuting the shingles into particles does not effectively reduce the tendency of the particles to stick together as was believed, Col. 5, lines 16-25, unless the particles are used shortly after the shredding process.
In shredding the shingles, because of economic concerns, it is desirable to shred the shingles in large batches at a central location, rather than to shred shingles at individual asphalt paving production plants, with the shredding often occurring at a location remote from the recycling plant. Because of this, the shredded shingles may sit in piles for an extended period of time and are often shipped in mass quantities. In storage and during shipment, the individual particles tend to stick or clump together due to the adhesive properties of the asphalt contained in the shingle particles. Thus, unless used soon after being shredded and without extensive transportation, the shredded shingles become difficult to stockpile, transport and use due to their tendency to clump or stick together. Therefore, a need exists in the art for a method of preparing shredded shingles so that they resist sticking or clumping together.